An overseas visitor is a person not normally resident in the United Kingdom. The National Health Service provides healthcare for people who live in the UK. People who do not normally live in this country are not automatically entitled to use the NHS free of charge.
This is regardless of their nationality, whether they hold a British passport, or have lived in and paid National Insurance contributions and taxes to this country in the past.
If you are a visitor to the UK, please make sure you have medical insurance to cover all NHS treatment during your time here. Also please ensure you have your valid European Health Insurance Card(EHIC) as this will need to be scanned for all NHS treatment including accident and emergency and minor injury departments.